THE QUESTION Might teenagers' behavior and lifestyle choices affect whether they have headaches?

THIS STUDY analyzed data on 5,847 teenagers, including how often they exercised, how much they weighed and whether they smoked. Among those who were overweight, smoked and did not exercise, about 55 percent had recurring headaches, compared with 25 percent of the teens who had none of these traits. Smoking alone raised the risk for headaches by 50 percent, being overweight increased it by 40 percent and not exercising raised it by 20 percent, when compared with teens who did not smoke, were not overweight and did exercise. Frequent headaches were nearly twice as common among teens with two negative behaviors and more than three times as frequent with three such behaviors.

WHO MAY BE AFFECTED? Teenagers. Physical activity often decreases as kids become teens. In the United States, an estimated 20 percent of high school students and 6 percent of middle school students smoke, and at least 20 percent are overweight or obese, according to the Centers for Disease Control and Prevention.

CAVEATS Data on the teens' behaviors came from their responses to questionnaires as well as from interviews and examinations. Other factors, such as socioeconomic and psychological status, were not considered and may have affected the results. The study did not test whether changing negative behaviors would reduce the frequency of headaches.

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.